This disclosure relates to a charging system for processing accounting information for communication sessions so that a communication service provider can charge subscribers for communication services and also provide charging status information to the subscriber. Various embodiments of the charging system and method for providing charging status information are provided for a communication service in which charging trigger functions from the communication network provide accounting information for a communication session to an offline charging subsystem (OFCS). In these embodiments, the charging system uses an OFCS and an online charging subsystem (OCS) to process the accounting information from the charging trigger functions, determine a charging status for the subscriber, and periodically communicate charging status information to the subscriber. The methods described herein may also be used to provide subscribers with charging status information for other types of communication services, other techniques for collecting accounting information from the communication network, and for other types of charging systems. For example, the charging system may include the functions for processing the accounting information for a communication session and providing charging status information to the subscriber of the corresponding communication service without necessarily including all of the functions of an OFCS or an OCS.
In long term evolution (LTE) networks, it is common to expect subscriber sessions that last from a couple of hours to a day or more. In such cases, it is inefficient to create a charging data record (CDR) at the end of the session, since it is very likely that the subscriber may have overshot the allocated quota of consumption (data volume or connection time or a combination involving both) and consequently, a different charging rate would have kicked in. A post facto alert to the subscriber is seldom considered a good choice, as it causes subscriber dissatisfaction and possible churn. It is required for the network to keep the subscriber informed about his/her consumption quantum, and if appropriate, provide a timely alert to the fact that continuation of an ongoing session is likely to be charged differentially and a session continuation is construed as a tacit subscriber concurrence to this differential charging. It is typical also to provide advance notification at a preset consumption % of the monthly consumption limits.
Handling post-paid service delivery poses the following problems: i) the concept of “quota reservation” using post-paid charging is not defined in the standards; ii) post-paid charging is not associated with typical “advice of charging” (AoC); iii) post-paid charging is near real-time; and iv) post-paid charging does not provide call control (such as service delivery termination upon low balance).
For LTE networks, the packet data network (PDN) gateway (PGW) and serving gateway (SGW) are in the data path, with the user equipment (UE) connecting via the SGW to the PGW and further on to the Internet. Therefore, the problem requires session accounting and AoC alerts working with the SGW/PGW. The subscription information, including applicable rates and quota allocation, is maintained in an OCS, such as an Instant Convergent Charging (ICC) Suite from Alcatel-Lucent of Paris, France. The OCS, for example, supports the Diameter Ro interface. Further complications may arise if the SGW and PGW do not support the Diameter Ro interface. The SGW and PGW, however, may have the Diameter Rf interface available, which is used for Diameter offline charging. If using this latter interface, a second issue is that standards do not have a definition for AoC notifications associated with offline charging. A related challenge is that offline charging is typically not required to rate a call or session in the standards. Rating is typically done by a separate rating engine (RE), which is invoked by a downstream billing mediation (BM) system. Last, but not the least, event-based charging is inefficient for long duration communication sessions, such as long duration LTE sessions, and there is a need to provide session-based charging which is capable of one or more mid-session evaluations on subscriber consumption of time/data volume and alerting the subscriber appropriately.
In the absence of an AoC mechanism, the subscriber is subjected to nasty surprises. As an example, consider the use case of a subscriber exceeding the allocated quota that she is allowed to consume on a monthly basis. For this case, suppose the rate plan for this subscriber is that she has a total of 1 GB per month for $10/month. Then for usage exceeding that she is charged $ 1/10 Mbyte. It is typical to expect the subscriber to get an alert upon reaching 90% of the usage threshold and having consumed 900 Mbytes, the subscriber would be notified via an e-mail or short message service (SMS). However, if the subscriber's data session lasts 12 hours and during that time the usage gets to 2 GB without a notification being sent, the subscriber would get a bill for $110 because she didn't receive fair warning of exceeding the usage threshold. Thus, an end-of-session notification, which can be arranged via a typical offline charging scenario, is inadequate and it would result in escalations. In most cases, the service provider would agree to withdraw the overage and bear the revenue leakage. While losing money on a single subscriber session may not be an issue, it is typical to have several million subscribers in the network and then this issue remains no longer a trivial issue. Therefore, what is needed is a way to overcome the shortcomings of the SGWs and PGWs and still be able to provide an end-user alert.
A potential alternative is to have the subscribers sign-off on an end user license agreement (EULA) that contains disclaimers about the inability to forewarn them appropriately and makes them responsible for the metered usage, which is reported after the session ends. While this may be a legal protection, by no means can it be imagined as something that promotes end-user satisfaction with the service provider.
Based on the foregoing, it is desirable for a charging system to provide charging status information to a subscriber of a communication service that charges different filling rates for different usage levels during a billing cycle. Moreover, it is desirable to provide such charging status information during a communication session. There is a particular need to provide such charging status information even when the charging trigger functions participating in the communication service provide accounting information that is compatible with an offline charging system.